Method of concentrating ores



Patented Oct. 25, 1938 I 4 UNITED STATES PATENT OFFICE No Drawing. Application March 2, 1937, Serial No. 128,669

This invention relates to the treatment of ores tures of advantage, some of which, with the forefor the beneficiation thereof. I going, will be set forth in the following descrip- In various of the known deposits of iron ore tion. In this description, for the purpose of examthroughout the world and in particular those of me, there is set forth the best embodiment of f: the Missabe Range of the Lake Superior district, the invention now known, but such embodiment there are large bodies of ore which have physical is to be regarded as typical only of many possible characteristics making them heretofore undesirembodiments, and the invention is not to be limable or unsatisfactory as sources for the manuited thereto. The present invention is of parfacture of pig iron. The Missabe Range contains ticular value in the treatment of certain.types large deposits of two typesof ore which it has of iron ores which have hitherto been considered, hitherto been uneconomical to utilize. The Misbecause of theirphysical conditiomeither impossabe ores are mainly soft and hydrated hematites sible of utilization for the extraction of their iron and limonite, and they vary in condition from very content, or uneconomical for such purpose befine dust to fairly coarse and granular ore and cause of the prohibitive cost of correcting and 15 there are also large quantities of so-called sandy handling them,

ores. The dusty and sandy ores'tend to choke up In a broad aspect the treatment herein for wet the reducing furnace and they also give rise to ores from which the free moisture will not readily large amounts of flue dust. For these reasons evaporate naturally consists in intimately mixing they are considered not very attractive as sources with such ores a water absorbent medium which for the production of pig iron. has an affinity for the\water of the ore greater .20 Another type of ore, of which there are large than that of the ore for the water and from which quantities in the Missabe Range particularly, is medium water will evaporate. In other words, the very wet or muddy type which has hitherto the ore is treated with a material that will draw been considered practically valueless because of the water out of the ore in a manner which may the low concentration of iron due to the presence be'conveniently referred to as capillary action. of considerable water. Water or moisture adds The water is then allowed to evaporate from the to the weight of ore to be transported. Some of absorbent medium leaving a relatively dry mix.- the soft ores of the Lake Superior region contain ture or agglomeration of dehydrated ore and dried as much as 9% of their weight as hygroscopic absorbent medium. It is found as a P Of the 139 water, and some as much as 25%. This moisture invention, that a highly satisfactory absorbent 3 content is quite constant under varying weather medium havingthe above described and other deconditions. Since the moisture is distributed sirable characteristics, is cement, preferably Portevenly throughoutthe ore, it does not evaporate land cement.

readily and the added cost of transporting and In practice, there is added to the crude wet ore 3-3 handling so much moisture makes these ores very as it comes from the mine, about 6% by weight 3 uneconomical. It has been proposed to remove of Portland cement. The materials are then the excess'water by sintering, but the cost of so thoroughly mixed such as in an ordinary cement doing is generally prohibitively high. mixer or other suitable apparatus, carebeing The prime object of the present-invention is taken not to exert any substantial crushing ac- 4'.) to provide for dehydrating such ores or freeing fi and the mixture is then Sp dut n e t from the water content thereof in a simground, floor or other, suitable surface in a relaple, inexpensive, expeditious and eminently sattively thin layer. In a'shed at ordinaryatmosisfactory manner, so as to reduce the weight of a pheric temperatures it is found that the material given amount of ore and thus facilitate the hanwill" dry and that a substantial amount of the 4 dling, transportation and storage of the treated free or suspended moisture will evaporate in about ore while at the same time putting the ore in a twenty-four hours. The setting and drying of condition for satisfactory and economical reducthe material may be hastened by the application ing in a blast or other reducing furnace. of a relatively small amount of heat. It is gen- A further object is to provide for the beneficiaerally preferable not to heat the mixture above tion of ores in a manner which is effective not 2 F; and it is found that the most economically only for the correction of the ores, but which will satisfactory drying temperature is around 200 F.

extend influence and benefits to the reducing op- Heating above 212 F. tends .to drive off the water eration for the extraction of the desired mineral of crystallization, which is not desirable, and may constituents of the ore. also exert some destructive effect upon the chem- The invention possesses other objects and feaical composition of the ore by its converting ac- 5 2 a,is4,1os

the iron mineral contained therein.v The ore is nuxing properties oi ordinary limestone which is naturally from said ore. It is found, however, basic flux in the blast furnace,

that the moisture in the ore has a greater aflin- As an example of the concentrating elects oi ity for cement than for the ore particles, and. I the present method 01' benei'iciation, the followwhen about 6% by weight 01' Portland cement ing tables are illustrative: is thoroughly mixed with the ore, practically all Table 1' represents an flnalysis 0! atypical of the tree moisture is absorbed by the cement wet and muddy hematite ore or limonite ore material and it will then readily evaporate from carrying by weight of free or suspended the cement, leaving the ore dehydrated or with water and in which the concentration of M0,, cientiy free from water that it may be economithe desired mineral, is only 57.12%. cally and satisfactorily utilized. Table 2 is an analysis of the dried or set mate- 20 The exact nature of this action and-the manrial resulting from the admixture with an ore by the cement in thehydration reaction. Howto constitute 67.12% and forming a material of granular form approaching a gravel-like condicomprises a method or "fitment for the bene change in the physical condition or structure of w is claimed The cement surrounds and coats each inditam undesirable amounts of ms c water viduai particle of ore and it is not desirable to and f changing the. form g appprgacmnz ream]? broken up for transportation to and hygroscopic water and thereby eflecting concenducmg the blast furnacetration of the ore, and whereby elimination of The above described treatment Wm water and hardening of the cement causes the practically all of the free or suspended water so treated ore t name a granular condition to have entirely lost the major portion of its I water content and the weight .01 the material t 1 1 Table 2 correspondingly decreased. Possibly, thismay b Per cent a Per cent due to continuing evaporation oi water from adby 8 y weilht .ia'cent the outside surface of the ccmentvcoating F920: 57-12 F820: 67.12 of the ore particle accompanied by the conse- 0 S10: 9.40 quent ability and strong tendency of the cement MnOz 1.60 MnO: 180 l to take up from the ore particle more water to A1201 8 A: 7.00 I replace that lost by evaporation. A noticeable I Ignition 8 loss 8.00 change inthe wet ores after the hereindescribed H20 20.00, Cement 6.00 treatment with cement occurs in the physical character or structure of the ore, which is 1 0-00 1100.00 

